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* [[List of all comics]] contains a complete table of all xkcd comics so far and the corresponding explanations. The red links ([[like this]]) are missing explanations. Feel free to help out by creating them! '''[[Help:How to add a new comic explanation|Here's how]]'''.

Latest comic

Title text: For a while, some physicists worked on a theory unifying the other forces with both the force of gravity and the film "Gravity," but even after Alfonso Cuarón was held in a deep underground chamber of water for 10^31 years he refused to sell his film to Disney.

Explanation

In physics, the fundamental interactions, also known as fundamental forces, are the interactions that do not appear to be reducible to more basic interactions. There are four fundamental interactions known to exist: the gravitational and electromagnetic interactions, which produce significant long-range forces whose effects can be seen directly in everyday life, and the strong and weak interactions, which produce forces at minuscule, subatomic distances and govern nuclear interactions. Some scientists speculate that a fifth force might exist, but, if so, it is not widely accepted nor proven.

This comic lists five physical forces (it split up electricity and magnetism), but also includes a number of other things (two countries and three businesses) that are known for "unifying" in a non-physics sense. East and West Germanyunited politically in 1990, more than forty years after being divided at the end of World War II. Entertainment company Disney has united in a business sense with a number of others over the years; the comic mentions animation studio Pixar and the Star Wars franchise. The comic states that this is the progress toward unifying the fundamental forces of nature, which is absurd, with the addition of Disney and Germany, both which are not one of the fundamental forces.[citation needed] Star Wars is, of course, all about The Force, but this has, for some reason, gone unnoticed by most physicists.

The title text jokes that some physicist tried to unify the force of gravity with the 2013 movie Gravity, starring Sandra Bullock. Of course, this is also absurd, but it turns out that this is just another jab by Randall at George Lucas for selling his rights to Star Wars to Disney. The jab comes when he makes it clear that the director of GravityAlfonso Cuarón would refuse to sell the rights to his film to Disney, even if he was held in underground chamber of water for 1031 years.

This water chamber and incredible time span is a reference to Proton decay, which is being investigated by trying to detect the Cherenkov radiation that could occur from possible decay of protons in water. These measurements are being conducted in immense water tanks buried under mountains to protect them against similar signals that could result from cosmic radiation. The same type of tanks have been used to detect neutrinos.

The half life of protons is currently believed to be between 1031-1036 years. This should be compared to the age of the universe at around 1.3 1010 years, which means that one second compared to the age of the universe is larger than the smallest suggested half life of the proton (as used in the comic) compared to the age of the universe, by a factor of about 10,000, but even this time would not make Cuarón cave in...

Unifications

Item

Unifications

Electricity

Electricity and magnetism were historically considered separate forces. Observations through the 19th century indicated that the two were closely linked, however, and the work of James Clerk Maxwell finally established their common identity in 1873. Today, their unified explanation, electromagnetism, is considered one of the four fundamental interactions in physics.

The unification of electromagnetism and the weak nuclear force—known as the electroweak interaction—is the only currently-accepted unification of two fundamental forces. Two Nobel Prizes in Physics have been awarded for work on this unification, in 1979 and in 1999.

Magnetism

Weak force

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Strong force

The strong nuclear force is similar to the electroweak forces, as they are all part of the model known as quantum field theory (QFT). There have been attempts to unify them to produce a so-called Grand Unified Theory. No model of their unification has yet been shown to be correct, and it remains a major unsolved problem in physics.

Gravity

Unlike the other three fundamental forces, gravity is not described by QFT, but by general relativity (GR). A so-called "Theory of Everything", describing both QFT and GR, could also unify gravity and the other forces. Such a unification is still strictly hypothetical, however.

East Germany

In 1945, after Nazi Germany's defeat in the Second World War, Germany was occupied by the Allied Forces. At first, it was expected that the whole country would be transitioned to a single post-war government, but but political and ideological differences between the Soviet Union and the other allies (which developed into the Cold War) prevented this. The Soviet-controlled zone became the German Democratic Republic, or East Germany, while the British, American and French zones of control merged to form the Federal Republic of Germany, or West Germany.

With the fall of the Berlin Wall (a physical and symbolic representation of the division) in 1989, and the fall of the East German socialist government in the "Peaceful Revolution", German reunification again became an immediate possibility. By late 1990, the merger was achieved, with East Germany joining the federal structure already existing in West Germany.

Just under two weeks before this comic appeared, on 2018-02-05, the Berlin Wall had been "gone as long as it had stood", namely 28 years, two months, and 27 days.

West Germany

Disney

Pixar was originally a part of the computer division of Lucasfilm, but was spun off into a separate business in 1986. The studio had a positive partnership with Walt Disney Animation, which resulted in a deal for Pixar to produce animated feature films for Walt Disney Pictures. Though the partnership later became strained, Disney agreed to buy Pixar in 2006. Pixar films produced after this acquisition have been branded "Disney-Pixar" films.

The Star Wars franchise was perhaps the most successful and best-known property of Lucasfilm, the company founded by George Lucas in 1971. Discussion in 2011 of a distribution deal with Disney, around the time that Lucas was planning his retirement, turned into the outright purchase of Lucasfilm by Disney in 2012. Since then, Disney has extensively revamped and developed the Star Wars franchise, with three new films and a television series released by the date of this comic, and several more in the works.

Pixar

Star Wars

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Transcript

[Ten rounded frames with text inside are shown in two rows. Below each frame there is a line going down and then this line either joins with one or two of the other frames lines or in two cases do not joins with any other. At the bottom of the panel the now five remaining lines turn towards the center of the bottom of the panel and ends in arrows that points towards three question marks. The first three frames' lines are unified, same goes for the next two, and the three after that. The lines of the last two are not joined with any other lines. The text in the transcript is given as it appears from left to right, disregarding if it is the top or bottom row, but this will alternate through the ten frames, starting with one up, then one down etc.]

Last 7 days (Top 10)

Lots of people contribute to make this wiki a success. Many of the recent contributors, listed above, have just joined. You can do it too! Create your account here.

You can read a brief introduction about this wiki at explain xkcd. Feel free to sign up for an account and contribute to the wiki! We need explanations for comics, characters, themes, memes and everything in between. If it is referenced in an xkcd web comic, it should be here.

List of all comics contains a complete table of all xkcd comics so far and the corresponding explanations. The red links (like this) are missing explanations. Feel free to help out by creating them! Here's how.

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